Allow setting the label cache size

src/ol/structs/LRUCache.js

@@ -267,6 +267,16 @@ LRUCache.prototype.set = function(key, value) {
 };
 
 
+/**
+ * Set a maximum number of entries for the cache.
+ * @param {number} size Cache size.
+ * @api
+ */
+LRUCache.prototype.setSize = function(size) {
+  this.highWaterMark = size;
+};
+
+
 /**
  * Prune the cache.
  */